1. Technical Field
The present invention relates to a piezoelectric element, a liquid-ejecting head including the piezoelectric element, and a liquid-ejecting apparatus including the piezoelectric element. The piezoelectric element includes a piezoelectric layer and electrodes through which a voltage is applied to the piezoelectric layer. The piezoelectric element produces a pressure change in a pressure-generating chamber in communication with a nozzle opening.
2. Related Art
One example of piezoelectric elements for use in liquid-ejecting heads includes a piezoelectric layer between two electrodes. The piezoelectric layer is formed of a piezoelectric material having an electromechanical transfer function, such as a crystallized dielectric material. Such a piezoelectric element can be mounted on a liquid-ejecting head as an actuator in a flexural vibration mode. One representative example of liquid-ejecting heads is an ink jet print head. The ink jet print head has a diaphragm as part of a pressure-generating chamber, which communicates with a nozzle opening for ejecting ink droplets. The diaphragm is deformed by a piezoelectric element to pressurize ink in the pressure-generating chamber, thereby ejecting ink droplets from the nozzle opening. A piezoelectric element for use in such an ink jet print head can be manufactured by forming a uniform piezoelectric layer over the entire surface of a diaphragm by a film-forming technique and dividing the piezoelectric layer by lithography into pieces corresponding to each individual pressure-generating chamber.
Examples of the piezoelectric material for such a piezoelectric element include, but are not limited to, lead zirconate titanate (PZT) (JP-A-2001-223404).
However, lead zirconate titanate (PZT) contains lead. Thus, from the standpoint of environmental protection, there is a demand for a piezoelectric material of a lead-free ferroelectric substance. Examples of the lead-free piezoelectric material include, but are not limited to, BiFeO3, which has a perovskite structure ABO3. However, BiFeO3-based piezoelectric materials have low insulating capacity and sometimes generate leakage current. Although commonly used lead zirconate titanate has been modified to improve its characteristics, the behavior of BiFeO3-based piezoelectric materials is unknown. These problems are not confined to liquid-ejecting heads, including ink jet print heads, and also occur in piezoelectric elements, such as actuators, contained in other apparatuses.